Recent studies indicate that the effect of voicing on the ear advantage in dichotic listening might serve as indicator of the development of speech processing abilities in children. In the present longitudinal study, we tested this idea by applying dichotic listening with voiced and unvoiced consonant-vowel syllables. In 35 boys and girls, tested at the age of 5, 6, 7, and 8 years, we found that the effect of voicing increases with age, and that girls were more affected by the voicing characteristics than boys. These results indicate a sex difference in the development of speech processing abilities.